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<title>What Is an Enterprise Bean? - The Java EE 6 Tutorial</title>
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      <td width="400px"><p class="toc level1"><a href="docinfo.html">Document Information</a></p>
<p class="toc level1 tocsp"><a href="gexaf.html">Preface</a></p>
<p class="toc level1 tocsp"><a href="gfirp.html">Part&nbsp;I&nbsp;Introduction</a></p>
<p class="toc level2"><a href="bnaaw.html">1.&nbsp;&nbsp;Overview</a></p>
<p class="toc level2"><a href="gfiud.html">2.&nbsp;&nbsp;Using the Tutorial Examples</a></p>
<p class="toc level1 tocsp"><a href="bnadp.html">Part&nbsp;II&nbsp;The Web Tier</a></p>
<p class="toc level2"><a href="bnadr.html">3.&nbsp;&nbsp;Getting Started with Web Applications</a></p>
<p class="toc level2"><a href="bnaph.html">4.&nbsp;&nbsp;JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="giepx.html">5.&nbsp;&nbsp;Introduction to Facelets</a></p>
<p class="toc level2"><a href="gjddd.html">6.&nbsp;&nbsp;Expression Language</a></p>
<p class="toc level2"><a href="bnaqz.html">7.&nbsp;&nbsp;Using JavaServer Faces Technology in Web Pages</a></p>
<p class="toc level2"><a href="gjcut.html">8.&nbsp;&nbsp;Using Converters, Listeners, and Validators</a></p>
<p class="toc level2"><a href="bnatx.html">9.&nbsp;&nbsp;Developing with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkmaa.html">10.&nbsp;&nbsp;JavaServer Faces Technology Advanced Concepts</a></p>
<p class="toc level2"><a href="bnawo.html">11.&nbsp;&nbsp;Configuring JavaServer Faces Applications</a></p>
<p class="toc level2"><a href="gkiow.html">12.&nbsp;&nbsp;Using Ajax with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="gkhxa.html">13.&nbsp;&nbsp;Advanced Composite Components</a></p>
<p class="toc level2"><a href="bnavg.html">14.&nbsp;&nbsp;Creating Custom UI Components</a></p>
<p class="toc level2"><a href="bnafd.html">15.&nbsp;&nbsp;Java Servlet Technology</a></p>
<p class="toc level2"><a href="bnaxu.html">16.&nbsp;&nbsp;Internationalizing and Localizing Web Applications</a></p>
<p class="toc level1 tocsp"><a href="bnayk.html">Part&nbsp;III&nbsp;Web Services</a></p>
<p class="toc level2"><a href="gijti.html">17.&nbsp;&nbsp;Introduction to Web Services</a></p>
<p class="toc level2"><a href="bnayl.html">18.&nbsp;&nbsp;Building Web Services with JAX-WS</a></p>
<p class="toc level2"><a href="giepu.html">19.&nbsp;&nbsp;Building RESTful Web Services with JAX-RS</a></p>
<p class="toc level2"><a href="gjjxe.html">20.&nbsp;&nbsp;Advanced JAX-RS Features</a></p>
<p class="toc level2"><a href="gkojl.html">21.&nbsp;&nbsp;Running the Advanced JAX-RS Example Application</a></p>
<p class="toc level1 tocsp"><a href="bnblr.html">Part&nbsp;IV&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="gijsz.html">22.&nbsp;&nbsp;Enterprise Beans</a></p>
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<p class="toc level3"><a href="">What Is an Enterprise Bean?</a></p>
<p class="toc level4"><a href="#giplk">Benefits of Enterprise Beans</a></p>
<p class="toc level4"><a href="#gipkn">When to Use Enterprise Beans</a></p>
<p class="toc level4"><a href="#gipnm">Types of Enterprise Beans</a></p>
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<p class="toc level3 tocsp"><a href="gipjg.html">What Is a Session Bean?</a></p>
<p class="toc level4"><a href="gipjg.html#gipkr">Types of Session Beans</a></p>
<p class="toc level5"><a href="gipjg.html#gipnl">Stateful Session Beans</a></p>
<p class="toc level5"><a href="gipjg.html#gipin">Stateless Session Beans</a></p>
<p class="toc level5"><a href="gipjg.html#gipim">Singleton Session Beans</a></p>
<p class="toc level4 tocsp"><a href="gipjg.html#gipmt">When to Use Session Beans</a></p>
<p class="toc level3 tocsp"><a href="gipko.html">What Is a Message-Driven Bean?</a></p>
<p class="toc level4"><a href="gipko.html#gipmj">What Makes Message-Driven Beans Different from Session Beans?</a></p>
<p class="toc level4"><a href="gipko.html#gipjx">When to Use Message-Driven Beans</a></p>
<p class="toc level3 tocsp"><a href="gipjf.html">Accessing Enterprise Beans</a></p>
<p class="toc level4"><a href="gipjf.html#girfl">Using Enterprise Beans in Clients</a></p>
<p class="toc level5"><a href="gipjf.html#girgn">Portable JNDI Syntax</a></p>
<p class="toc level4 tocsp"><a href="gipjf.html#gipiz">Deciding on Remote or Local Access</a></p>
<p class="toc level4"><a href="gipjf.html#gipmz">Local Clients</a></p>
<p class="toc level5"><a href="gipjf.html#gipsc">Accessing Local Enterprise Beans Using the No-Interface View</a></p>
<p class="toc level5"><a href="gipjf.html#gipse">Accessing Local Enterprise Beans That Implement Business Interfaces</a></p>
<p class="toc level4 tocsp"><a href="gipjf.html#gipiu">Remote Clients</a></p>
<p class="toc level4"><a href="gipjf.html#gipkd">Web Service Clients</a></p>
<p class="toc level4"><a href="gipjf.html#giply">Method Parameters and Access</a></p>
<p class="toc level5"><a href="gipjf.html#giplx">Isolation</a></p>
<p class="toc level5"><a href="gipjf.html#gipkv">Granularity of Accessed Data</a></p>
<p class="toc level3 tocsp"><a href="gipio.html">The Contents of an Enterprise Bean</a></p>
<p class="toc level4"><a href="gipio.html#gipnz">Packaging Enterprise Beans in EJB JAR Modules</a></p>
<p class="toc level4"><a href="gipio.html#gippi">Packaging Enterprise Beans in WAR Modules</a></p>
<p class="toc level3 tocsp"><a href="gipks.html">Naming Conventions for Enterprise Beans</a></p>
<p class="toc level3"><a href="giplj.html">The Lifecycles of Enterprise Beans</a></p>
<p class="toc level4"><a href="giplj.html#gipln">The Lifecycle of a Stateful Session Bean</a></p>
<p class="toc level4"><a href="giplj.html#giplm">The Lifecycle of a Stateless Session Bean</a></p>
<p class="toc level4"><a href="giplj.html#giprx">The Lifecycle of a Singleton Session Bean</a></p>
<p class="toc level4"><a href="giplj.html#gipkw">The Lifecycle of a Message-Driven Bean</a></p>
<p class="toc level3 tocsp"><a href="giplg.html">Further Information about Enterprise Beans</a></p>
<p class="toc level2 tocsp"><a href="gijre.html">23.&nbsp;&nbsp;Getting Started with Enterprise Beans</a></p>
<p class="toc level2"><a href="gijrb.html">24.&nbsp;&nbsp;Running the Enterprise Bean Examples</a></p>
<p class="toc level2"><a href="bnbpk.html">25.&nbsp;&nbsp;A Message-Driven Bean Example</a></p>
<p class="toc level2"><a href="gkcqz.html">26.&nbsp;&nbsp;Using the Embedded Enterprise Bean Container</a></p>
<p class="toc level2"><a href="gkidz.html">27.&nbsp;&nbsp;Using Asynchronous Method Invocation in Session Beans</a></p>
<p class="toc level1 tocsp"><a href="gjbnr.html">Part&nbsp;V&nbsp;Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="giwhb.html">28.&nbsp;&nbsp;Introduction to Contexts and Dependency Injection for the Java EE Platform</a></p>
<p class="toc level2"><a href="gjbls.html">29.&nbsp;&nbsp;Running the Basic Contexts and Dependency Injection Examples</a></p>
<p class="toc level2"><a href="gjehi.html">30.&nbsp;&nbsp;Contexts and Dependency Injection for the Java EE Platform: Advanced Topics</a></p>
<p class="toc level2"><a href="gkhre.html">31.&nbsp;&nbsp;Running the Advanced Contexts and Dependency Injection Examples</a></p>
<p class="toc level1 tocsp"><a href="bnbpy.html">Part&nbsp;VI&nbsp;Persistence</a></p>
<p class="toc level2"><a href="bnbpz.html">32.&nbsp;&nbsp;Introduction to the Java Persistence API</a></p>
<p class="toc level2"><a href="gijst.html">33.&nbsp;&nbsp;Running the Persistence Examples</a></p>
<p class="toc level2"><a href="bnbtg.html">34.&nbsp;&nbsp;The Java Persistence Query Language</a></p>
<p class="toc level2"><a href="gjitv.html">35.&nbsp;&nbsp;Using the Criteria API to Create Queries</a></p>
<p class="toc level2"><a href="gkjiq.html">36.&nbsp;&nbsp;Creating and Using String-Based Criteria Queries</a></p>
<p class="toc level2"><a href="gkjjf.html">37.&nbsp;&nbsp;Controlling Concurrent Access to Entity Data with Locking</a></p>
<p class="toc level2"><a href="gkjia.html">38.&nbsp;&nbsp;Improving the Performance of Java Persistence API Applications By Setting a Second-Level Cache</a></p>
<p class="toc level1 tocsp"><a href="gijrp.html">Part&nbsp;VII&nbsp;Security</a></p>
<p class="toc level2"><a href="bnbwj.html">39.&nbsp;&nbsp;Introduction to Security in the Java EE Platform</a></p>
<p class="toc level2"><a href="bncas.html">40.&nbsp;&nbsp;Getting Started Securing Web Applications</a></p>
<p class="toc level2"><a href="bnbyk.html">41.&nbsp;&nbsp;Getting Started Securing Enterprise Applications</a></p>
<p class="toc level1 tocsp"><a href="gijue.html">Part&nbsp;VIII&nbsp;Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="gijto.html">42.&nbsp;&nbsp;Introduction to Java EE Supporting Technologies</a></p>
<p class="toc level2"><a href="bncih.html">43.&nbsp;&nbsp;Transactions</a></p>
<p class="toc level2"><a href="bncjh.html">44.&nbsp;&nbsp;Resource Connections</a></p>
<p class="toc level2"><a href="bncdq.html">45.&nbsp;&nbsp;Java Message Service Concepts</a></p>
<p class="toc level2"><a href="bncgv.html">46.&nbsp;&nbsp;Java Message Service Examples</a></p>
<p class="toc level2"><a href="gkahp.html">47.&nbsp;&nbsp;Advanced Bean Validation Concepts and Examples</a></p>
<p class="toc level2"><a href="gkeed.html">48.&nbsp;&nbsp;Using Java EE Interceptors</a></p>
<p class="toc level1 tocsp"><a href="gkgjw.html">Part&nbsp;IX&nbsp;Case Studies</a></p>
<p class="toc level2"><a href="gkaee.html">49.&nbsp;&nbsp;Duke's Tutoring Case Study Example</a></p>
<p class="toc level1 tocsp"><a href="idx-1.html">Index</a></p>
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<a name="gipmb"></a><h2>What Is an Enterprise Bean?</h2>
<p><a name="indexterm-1322"></a>Written in the Java programming language, an enterprise bean is a server-side component
that encapsulates the business logic of an application. The business logic is the
code that fulfills the purpose of the application. In an inventory control application,
for example, the enterprise beans might implement the business logic in methods called
<tt>checkInventoryLevel</tt> and <tt>orderProduct</tt>. By invoking these 32&ndash;bit methods, clients can access the inventory
services provided by the application.</p>



<a name="giplk"></a><h3>Benefits of Enterprise Beans</h3>
<p><a name="indexterm-1323"></a>For several reasons, enterprise beans simplify the development of large, distributed applications. First,
because the EJB container provides system-level services to enterprise beans, the bean developer
can concentrate on solving business problems. The EJB container, rather than the bean
developer, is responsible for system-level services, such as transaction management and security authorization.</p>

<p><a name="indexterm-1324"></a><a name="indexterm-1325"></a>Second, because the beans rather than the clients contain the application&rsquo;s business logic, the
client developer can focus on the presentation of the client. The client developer
does not have to code the routines that implement business rules or access
databases. As a result, the clients are thinner, a benefit that is particularly
important for clients that run on small devices.</p>

<p>Third, because enterprise beans are portable components, the application assembler can build new
applications from existing beans. Provided that they use the standard APIs, these applications
can run on any compliant Java EE server.</p>



<a name="gipkn"></a><h3>When to Use Enterprise Beans</h3>
<p>You should consider using enterprise beans if your application has any of the
following requirements.</p>


<ul><li><p>The application must be scalable. To accommodate a growing number of users, you may need to distribute an application&rsquo;s components across multiple machines. Not only can the enterprise beans of an application run on different machines, but also their location will remain transparent to the clients.</p>

</li>
<li><p>Transactions must ensure data integrity. Enterprise beans support transactions, the mechanisms that manage the concurrent access of shared objects.</p>

</li>
<li><p>The application will have a variety of clients. With only a few lines of code, remote clients can easily locate enterprise beans. These clients can be thin, various, and numerous.</p>

</li></ul>


<a name="gipnm"></a><h3>Types of Enterprise Beans</h3>
<p><a name="indexterm-1326"></a><a href="#giplz">Table&nbsp;22-1</a> summarizes the two types of enterprise beans. The following sections discuss each
type in more detail.</p>

<a name="giplz"></a><p class="caption">Table&nbsp;22-1 Enterprise Bean Types</p><table><col width="29%"><col width="70%"><tr><th align="left" valign="top" scope="column"><p>Enterprise Bean Type</p>

</th>
<th align="left" valign="top" scope="column"><p>Purpose</p>

</th>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Session</p>

</td>
<td align="left" valign="top" scope="row"><p><a name="indexterm-1327"></a><a name="indexterm-1328"></a>Performs a task for a client; optionally, may implement
a web service</p>

</td>
</tr>
<tr><td align="left" valign="top" scope="row"><p>Message-driven</p>

</td>
<td align="left" valign="top" scope="row"><p>Acts as a listener for a particular messaging type, such
as the Java Message Service API</p>

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